This invention relates generally to supported catalysts, and more particularly to supported metallocene catalysts and methods for their production and use.
Metallocene catalyst systems and their use for olefin polymerization are well known. Metallocene catalysts are single-sited and differently activated compared to conventional Ziegler-Natta catalysts. A typical metallocene catalyst system includes a metallocene catalyst, a support, and an activator. Upon attaching or xe2x80x9cfixingxe2x80x9d the catalyst to the support, the catalyst is generally referred to as a supported catalyst. For many polymerization processes, supported catalysts are required, and various methods for attaching metallocene catalysts to a support are known in the art. Supports suitable for use with metallocene catalyst are generally porous materials and can include organic materials, inorganic materials and inorganic oxides.
However, many supports contain reactive functionalities. In some instances, these reactive functionalities may deactivate or reduce the activity of the catalyst fixed to the support. When this occurs, the addition of more catalyst to the catalyst system may be necessary to ensure sufficient polymer production during olefin polymerization. Increasing the catalyst concentration in the catalyst system to compensate for activity reduction caused by reactive functionalities is generally undesirable for many reasons. For instance, generally the addition of more catalyst may also require the addition of more activator. As such, increasing the concentrations of both catalyst and activator to overcome the effects of catalyst deactivation by reactive functionalities substantially increases the cost of olefin polymerization.
Hydroxyl groups are an example of a reactive functionality present on some supports which deactivate metallocene catalysts. Hydroxyl groups are present on supports, such as inorganic oxides. An example of an inorganic oxide is silica gel. As such, when using silica gel to support a metallocene catalyst, it is desirable to remove, reduce or render inactive a sufficient number of the hydroxyl groups. Methods of removing or reducing hydroxyl groups include thermal and/or chemical treatments. The removal of hydroxyl groups is known as dehydroxylation.
Thermally treating or heating the support material generally avoids contamination of the support by undesirable chemicals. However, in the case of many porous supports, such as silica gel, heating the support may fail to achieve sufficient dehydroxylation. Chemically treating the support material can be expensive and may result in contamination of the support.
Thus, there remains a need for increasing the activity of supported metallocene catalyst systems. Particularly, there remains a need for improved supported metallocene catalysts wherein the reactive functionalities of the support are reduced and/or deactivated.
The present invention provides a highly active metallocene supported catalyst composition. Generally, the inventor has discovered that when at least one metallocene catalyst is bound to a fluorided support, the activity of this metallocene supported catalyst composition is higher compared to the activity of the same metallocene catalyst bound to a non-fluorided support. These non-fluorided supports included supports to which no fluorine was added or a halide other than fluorine was added.
In one embodiment, the metallocene supported catalyst composition includes a metallocene catalyst and a support composition. The support composition may be represented by the formula: Sup F, wherein Sup is a support, and F is a fluorine atom bound to the support. The support composition may be a fluorided support composition.
In another embodiment, the metallocene supported catalyst composition includes a support composition represented by the formula: Sup L Fn. xe2x80x9cSupxe2x80x9d may further be defined as a support selected from the group which includes talc, clay, silica, alumina, magnesia, zirconia, iron oxides, boria, calcium oxide, zinc oxide, barium oxide, thoria, aluminum phosphate gel, polyvinylchloride and substituted polystyrene and mixtures thereof.
xe2x80x9cLxe2x80x9d is a first member selected from the group which includes (i) bonding, sufficient to bound the F to the Sup; (ii) B, Ta, Nb, Ge, Ga, Sn, Si, P, Ti, Mo, Re, or Zr bound to the Sup and to the F; and (iii) O bound to the Sup and bound to a second member selected from the group consisting of B, Ta, Nb, Ge, Ga, Sn, Si, P, Ti, Mo, Re, or Zr which is bound to the F;
xe2x80x9cFxe2x80x9d is a fluorine atom; and
xe2x80x9cnxe2x80x9d is a number from 1-7.
The support composition desirably may be a fluorided support composition. The metallocene supported catalyst composition may also include boron and may also include an activator, such as alkylalumoxane or MAO or haloaryl boron or aluminum compounds.
The metallocene catalyst may be represented by the formula: CpmMRnXq, wherein Cp is a cyclopentadienyl ring which may be substituted, or derivative thereof which may be substituted, M is a Group 4, 5, or 6 transition metal, R is a hydrocarbyl group or hydrocarboxy group having from one to 20 carbon atoms, X may be a halide, a hydride, an alkyl group, an alkenyl group or an arylalkyl group, and m=1-3, n=0-3, q=0-3, and the sum of m+n+q is equal to the oxidation state of the transition metal.
The present invention also provides a method of making the metallocene supported catalyst composition. The method step includes contacting the metallocene catalyst with a support composition, desirably a fluorided support composition, under suitable conditions and for a sufficient time, wherein the support composition is represented by the formula Sup L Fn. The support composition, and particularly the fluorided support composition, may be made by contacting a hydroxyl group containing support material with at least one inorganic fluoride under suitable conditions and for a sufficient time wherein the fluoride becomes bound to the support.
The present invention also provides an olefin polymerization method. The steps of the olefin polymerization method include contacting a polymerizable olefin with the metallocene supported catalyst composition under suitable conditions and for a sufficient time. Desirably, the polymerizable material is propylene. The polymerizable olefin may be formed into numerous articles, such as, for example, films, fibers, fabrics, and molded structures.